OPENSSL_ia32cap final touches. Note that OPENSSL_ia32cap is no longer a

[openssl.git] / doc / crypto / OPENSSL_ia32cap.pod

diff --git a/doc/crypto/OPENSSL_ia32cap.pod b/doc/crypto/OPENSSL_ia32cap.pod
index 46afd1988083ed20de053fd6a0ede2dd23c3bc10..790e8e9b1ef2d120c6a55a2f5546274547be42f4 100644 (file)
--- a/doc/crypto/OPENSSL_ia32cap.pod
+++ b/doc/crypto/OPENSSL_ia32cap.pod
@@ -6,26 +6,26 @@ OPENSSL_ia32cap
 
 =head1 SYNOPSIS
 
- extern unsigned long OPENSSL_ia32cap;
- unsigned long *OPENSSL_ia32cap_loc();
+ unsigned long *OPENSSL_ia32cap_loc(void);
+ #define OPENSSL_ia32cap (*(OPENSSL_ia32cap_loc()))
 
 =head1 DESCRIPTION
 
-OPENSSL_ia32cap is a variable containing IA-32 processor capabilities
-bit vector as it appears in EDX register after executing CPUID
-instruction with EAX=1 input value (see Intel Application Note
-#241618). Naturally it's defined/meaningful on IA-32 platforms only.
-The variable is normally set up automatically upon toolkit
-initialization and can be manipulated afterwards to modify crypto
-library behaviour. For the moment of this writing only two bits are
-significant, namely bit #26 denoting SSE2 support, and bit #4 denoting
-presence of Time-Stamp Counter. Resetting bit #26 at run-time for
-example disables high-performance SSE2 code present in the crypto
+Value returned by OPENSSL_ia32cap_loc() is address of a variable
+containing IA-32 processor capabilities bit vector as it appears in EDX
+register after executing CPUID instruction with EAX=1 input value (see
+Intel Application Note #241618). Naturally it's meaningful on IA-32
+platforms only. The variable is normally set up automatically upon
+toolkit initialization, but can be manipulated afterwards to modify
+crypto library behaviour. For the moment of this writing only two bits
+are significant, namely bit #26 denoting SSE2 support, and bit #4
+denoting presence of Time-Stamp Counter. Clearing bit #26 at run-time
+for example disables high-performance SSE2 code present in the crypto
 library. You might have to do this if target OpenSSL application is
 executed on SSE2 capable CPU, but under control of OS which does not
-support SSE2 extentions. Even though you can programmatically
-manipulate the value, you most likely will find it more appropriate to
-set up an environment variable with the same name prior starting target
+support SSE2 extentions. Even though you can manipulate the value
+programmatically, you most likely will find it more appropriate to set
+up an environment variable with the same name prior starting target
 application, e.g. 'env OPENSSL_ia32cap=0x10 apps/openssl', to achieve
 same effect without modifying the application source code.
 Alternatively you can reconfigure the toolkit with no-sse2 option and